Magnetic tape cartridge

ABSTRACT

A magnetic tape cartridge includes a cartridge casing formed by upper and lower casing halves and a single reel around which a magnetic tape is wound and which is contained in the cartridge casing for rotation. A slide door for opening and closing a tape outlet opening is mounted on the cartridge casing to be linearly slidable along a door passage between a closing position where it closes the tape outlet opening and an opening position where it opens the tape outlet opening. A door spring for urging the slide door toward the closing position and holding the same in the closing position is disposed on the door passage.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] This invention relates to a magnetic tape cartridge comprising acartridge casing formed by upper and lower casing halves and a singlereel around which a magnetic tape is wound and which is contained in thecartridge casing for rotation, and more particularly to such as magnetictape cartridge provided with a slide door for opening and closing a tapeoutlet opening formed in the cartridge casing.

[0003] 2. Description of the Related Art

[0004] There has been known a single reel magnetic tape cartridgecomprising a flat cartridge casing which is formed by upper and lowercasing halves and is substantially square in shape and a single reelaround which a magnetic tape is wound and which is contained in thecartridge casing for rotation. Such a single reel magnetic tapecartridge has been used for retaining data of a computer or the like. Atape outlet opening is formed in a side wall of the cartridge casing andwhen the magnetic tape cartridge is used, i.e., when the magnetic tapecartridge is loaded in a recording and reproducing system as, forinstance, an external storage for a computer and information is to berecorded on the magnetic tape or information recorded on the magnetictape is to be read, the magnetic tape wound around the reel is drawn outthrough the tape outlet opening.

[0005] In such a magnetic tape cartridge of one type, a leader, block isfixed to the leading end of a leader tape which is connected to themagnetic tape and when the magnetic tape cartridge is not used, themagnetic tape is fully wound around the reel with the leader blockfitted in the tape outlet opening to close the tape outlet opening. Inthe case of the magnetic tape cartridge of this type, when the magnetictape cartridge is loaded in the recording and reproducing system, adrive means in the recording and reproducing system engages withengagement teeth on the reel exposed outside at the central portion ofthe lower casing half and a tape drawing mechanism in the recording andreproducing system chucks the leader block and draws the magnetic tapeoutside the cartridge casing into a tape running path of the recordingand reproducing system.

[0006] In another type, the tape outlet opening is closed and opened bya lid which is rotatable between a closing position where it closes thetape outlet opening and an opening position where it opens the tapeoutlet opening, the lid being urged by a spring toward the closingposition and locked in the closing position by a lid lock spring-urgedin the lock position. A hook member is fixed to the leading end of aleader tape which is connected to the magnetic tape and when themagnetic tape cartridge is not used, the magnetic tape is fully woundaround the reel with the hook member retracted inside the tape outletopening and the lid held in the closing position. In the case of themagnetic tape cartridge of this type, when the magnetic tape cartridgeis loaded in the recording and reproducing system, a drive means in therecording and reproducing system engages with engagement teeth on thereel exposed outside at the central portion of the lower casing half anda tape drawing mechanism in the recording and reproducing system movesthe lid to the opening position, chucks the hook member and draws themagnetic tape outside the cartridge casing into a tape running path ofthe recording and reproducing system.

[0007] The magnetic tape cartridge of the former type is advantageous inthat the tape drawing mechanism of the tape drive system may be simplein structure since the tape drawing mechanism has only to chuck theleader block and draws the same. However there is a problem that dust isapt to enter the cartridge casing through the space between the leaderblock and the tape outlet opening when the magnetic tape cartridge isnot used.

[0008] Though being free from the problem that dust is apt to enter thecartridge casing, the magnetic tape cartridge of the latter type isdisadvantageous in that the lid lock must be released and the lid mustbe opened, which complicates the structure of the tape drawingmechanism. Further the space for rotating the lid is required in thetape drive system, and at the same time, incorporation of the springsfor urging the lid and the lid lock in the cartridge casing takes alarge man-hour.

SUMMARY OF THE INVENTION

[0009] In view of the foregoing observations and description, theprimary object of the present invention is to provide a magnetic tapecartridge which is free from all the problems described above.

[0010] In accordance with the present invention, there is provided amagnetic tape cartridge comprising a cartridge casing formed by upperand lower casing halves and a single reel around which a magnetic tapeis wound and which is contained in the cartridge casing for rotation,

[0011] wherein the improvement comprises that a slide door for openingand closing a tape outlet opening is mounted on the cartridge casing tobe linearly slidable along a passage between a closing position where itcloses the tape outlet opening and an opening position where it opensthe tape outlet opening, and a door spring for urging the slide doortoward the closing position and holding the same in the closing positionis disposed on the passage of the slide door.

[0012] With this arrangement, the fear that dust enters the cartridgecasing through the tape outlet opening while the magnetic tape cartridgeis not used can be eliminated, and no space for permitting the slidedoor to move to the opening position is necessary in the tape drivesystem.

[0013] Further since the slide door is simply held in the closedposition by the door spring, the slide door can be opened by simplypushing the door overcoming the force of the door spring withoutreleasing a lock, whereby the tape drawing mechanism may be simple instructure.

[0014] In one embodiment of the present invention, guide grooves forguiding the upper end lower ends of the slide door along the passage areformed respectively on the upper and lower casing halves and the doorspring is in the form of a wire spring or a plate spring which is heldbetween the upper and lower casing halves at one end and abuts againstthe rear end face of the slide door at the other end.

[0015] A wall portion which prevents the door spring from beingdisengaged from the slide door while the slide is slid between theopening position and the closing position may be provided on thecartridge casing.

[0016] With this arrangement, incorporation of the door spring isfacilitated.

[0017] In another embodiment of the present invention, a closed spacedefining the passage of the slide door is formed between the upper andlower casing halves and the rear end face of the slide door and the doorspring in the form of a plate spring is disposed in the closed spacewith its ends in abutment against the end wall of the closed space andthe rear end face of the slide door, respectively.

[0018] With this embodiment, the door spring may be simply thrown in theclosed space, and accordingly incorporation of the door spring isextremely facilitated.

[0019] The door spring may be a coiled spring whose longitudinal axisextends in parallel to the direction of sliding movement of the slidedoor. In this case, it is preferred that the coiled spring be disposedin a space surrounded by ribs respectively extending from the upper andlower casing halves. With this arrangement, the door spring can be heldin place.

[0020] Further it is preferred that a bent portion against which thecoiled spring abuts be formed on a rear end portion of the slide door.With this arrangement, the coiled spring can be surely abuts against theslide door.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021]FIG. 1 is a perspective view showing a magnetic tape cartridge inaccordance with a first embodiment of the present invention with theslide door closed,

[0022]FIG. 2 is a perspective view showing the magnetic tape cartridgewith the slide door opened,

[0023]FIG. 3 is a fragmentary horizontal cross-sectional view showingthe arrangement of the slide door and the door spring of the magnetictape cartridge of the first embodiment,

[0024]FIG. 4A is a fragmentary vertical cross-sectional view showing thearrangement of the slide door and the door spring with the slide doorclosed,

[0025]FIG. 4B is a fragmentary vertical cross-sectional view showing thearrangement of the slide door and the door spring with the slide dooropened,

[0026]FIG. 5 is a cross-sectional view taken along line V-V in FIG. 4A,

[0027]FIG. 6A is a perspective view showing the rear end face of theslide door and the door spring when the door spring is of a platespring,

[0028]FIG. 6B is a perspective view showing the rear end face of theslide door and the door spring when the door spring is of a wire spring,

[0029]FIGS. 7A and 7B are views similar to FIGS. 4A and 4B but showing amodification of the arrangement of the slide door and the door spring,

[0030]FIG. 8 is a modification of the spring holding structure which canbe employed when the door spring is of a wire spring,

[0031]FIG. 9 is a modification of the spring holding structure which canbe employed when the door spring is of a wire spring,

[0032]FIG. 10 is a view similar to FIG. 3 but showing a spring holdingstructure in a magnetic tape cartridge in accordance with a secondembodiment of the present invention,

[0033]FIGS. 11A and 11B are vertical cross-sectional views showing thearrangement of the slide door and the door spring in the magnetic tapecartridge of the second embodiment,

[0034]FIG. 12 is a fragmentary cross-section view showing the springholding structure in the second embodiment,

[0035]FIG. 13 is a vertical cross-sectional view showing the arrangementof the slide door and the door spring in a magnetic tape cartridge of athird embodiment of the present invention,

[0036]FIG. 14 is a cross-sectional view taken along line XIV-XIV in FIG.13,

[0037]FIG. 15 is a fragmentary cross-sectional view showing amodification of the arrangement of the slide door and the door spring inthe third embodiment,

[0038]FIGS. 16A and 16B are views similar to FIGS. 4A and 4B but showinga fourth embodiment of the present invention,

[0039]FIGS. 17A and 17B are a rear perspective view and a rear side viewof the slide door in the fourth embodiment,

[0040]FIGS. 18A and 18B are views similar to FIGS. 17A and 17B butshowing a modification of the arrangement of the slide door and the doorspring,

[0041]FIG. 19 is a perspective view showing the arrangement of the slidedoor and the door spring in a fifth embodiment,

[0042]FIGS. 20A and 20B are views similar to FIGS. 4A and 4B but showinga sixth embodiment of the present invention,

[0043]FIGS. 21A and 21B are views similar to FIGS. 4A and 4B but showinga seventh embodiment of the present invention,

[0044]FIGS. 22A and 22B are views similar to FIGS. 21A and 21B butshowing an eighth embodiment of the present invention,

[0045]FIGS. 23A and 23B are views similar to FIGS. 21A and 21B butshowing a ninth embodiment of the present invention,

[0046]FIGS. 24A to 24D are front views of the arrangement of the doorspring and the slide door in a magnetic tape cartridge in accordancewith a tenth embodiment of the present invention with the slide door indifferent positions,

[0047]FIGS. 25A and 25B are views similar to FIGS. 21A and 21B butshowing a eleventh embodiment of the present invention,

[0048]FIG. 26 is a perspective view of the slide door employed in theeleventh embodiment,

[0049]FIG. 27 is a cross-sectional view taken along line XXVII-XXVII inFIG. 25A,

[0050]FIG. 28 is a cross-sectional view taken along line XXVIII-XXVIIIin FIG. 25B,

[0051]FIGS. 29A and 29B are views similar to FIGS. 21A and 21B butshowing a twelfth embodiment of the present invention,

[0052]FIG. 30 is a cross-sectional view taken along line XXX-XXX in FIG.29A,

[0053]FIG. 31 is a view for illustrating the effect of the twelfthembodiment,

[0054]FIGS. 32A and 32B are views similar to FIGS. 21A and 21B butshowing a thirteenth embodiment of the present invention,

[0055]FIG. 33 is a cross-sectional view taken along line XXXIII-XXXIIIin FIG. 32A,

[0056]FIGS. 34A to 34C are cross-sectional views taken along lines A-A,B-B and C-C in FIG. 33,

[0057]FIGS. 35A and 35B are views for illustrating the effect of thethirteenth embodiment,

[0058]FIG. 36 is a cross-sectional view showing a modification of thethirteenth embodiment,

[0059]FIG. 37 is a front view of the slide door in the modificationshown in FIG. 36,

[0060]FIG. 38 is a front view showing a modification of the springsupport rod,

[0061]FIGS. 39A to 39C are front views showing a modification of thespring support rod shown in FIG. 38,

[0062]FIG. 40 is a front view showing a modification of the coiledspring,

[0063]FIG. 41C is a fragmentary plan view of an important part of therod, FIG. 41B is a side view of the rod and FIG. 41C is a fragmentarycross-sectional view of an important part of the slide door when the rodis formed separately from the slide door,

[0064]FIG. 42 is a side view partly in cross-section showing the springsupport rod fixed to the slide door,

[0065]FIG. 43 is a perspective view showing incorporation of a door unitin the cartridge casing in a fourteenth embodiment of the presentinvention,

[0066]FIG. 44A is a front cross-sectional view showing the door unit ina state where the slide door is in a tacked state,

[0067]FIG. 44B is a front cross-sectional view showing the door unit ina state where the slide door is slidable,

[0068]FIG. 45 is a cross-sectional view taken along line A-A in FIG.44B,

[0069]FIG. 46A is a front view showing the door spring and the slidedoor in a magnetic tape cartridge in accordance with a fifteenthembodiment of the present invention,

[0070]FIG. 46B is a cross-sectional view of the door spring and theslide door,

[0071]FIG. 47B is a perspective view of the door spring,

[0072]FIG. 48A is a front view showing the door spring and the slidedoor in a magnetic tape cartridge in accordance with a seventeenthembodiment of the present invention,

[0073]FIG. 48B is a front view showing a modification of the door springand the slide door shown in FIG. 48A,

[0074]FIG. 49 is an exploded perspective of the spring shown in FIG.48A,

[0075]FIGS. 50A to 50C are views for illustrating the effect of theseventeenth embodiment,

[0076]FIGS. 51A and 51B are views similar to FIGS. 21A and 21B butshowing an eighteenth embodiment of the present invention,

[0077]FIGS. 52A to 52C are views showing modifications of the elasticbody,

[0078]FIG. 53 is a fragmentary cross-sectional view showing an importantpart of the magnetic tape cartridge in accordance with a nineteenthembodiment of the present invention,

[0079]FIG. 54 is a view similar to FIG. 53 for illustrating theoperation of the locking mechanism,

[0080]FIGS. 55 and 56 are views similar to FIG. 53 but showingmodifications of the nineteenth embodiment,

[0081]FIG. 57 is a fragmentary cross-sectional view showing an importantpart of the magnetic tape cartridge in accordance with a twentiethembodiment of the present invention,

[0082]FIGS. 58 and 59 are views for illustrating the operation of thelicking mechanism,

[0083]FIG. 60 is a fragmentary cross-sectional view showing an importantpart of the magnetic tape cartridge in accordance with a twenty-firstembodiment of the present invention,

[0084]FIG. 61 is a perspective view showing the slide door in a magnetictape cartridge in accordance with a twenty-second embodiment of thepresent invention,

[0085] FIGS. 62 to 66 are perspective views showing the modification ofthe slide door shown in FIG. 61,

[0086]FIG. 67 is a fragmentary cross-sectional view showing an importantpart of the slide door shown in FIG. 66 and the sliding surface of theslide door passage,

[0087]FIGS. 68 and 69 are perspective views showing other modificationsof the slide door shown in FIG. 61,

[0088]FIGS. 70 and 71 are views similar to FIG. 67 but showing stillother modifications of the slide door shown in FIG. 61,

[0089]FIG. 72A is a front view of the slide door employed in themagnetic tape cartridge in accordance with a twenty-third embodiment ofthe present invention,

[0090]FIG. 72B is a plan view of the slide door,

[0091]FIG. 72C is a cross-sectional view taken along line A-A in FIG.72A,

[0092]FIG. 72D is a side view of the slide door,

[0093]FIG. 73 is an enlarged perspective view of a part of the magnetictape cartridge shown in FIG. 1,

[0094]FIG. 74 is a perspective view of the slide door,

[0095]FIG. 75 is a perspective view of a modification of the slide door,and

[0096]FIG. 76 is an enlarged perspective view of a part of the magnetictape cartridge in which the slide door shown in FIG. 75 is employed.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0097] A magnetic tape cartridge in accordance with a first embodimentof the present invention will be described with reference to FIGS. 1 to9, hereinbelow. In FIGS. 1 and 2, the magnetic tape cartridge inaccordance with the first embodiment of the present invention comprisesa cartridge casing 1 formed by upper and lower casing halves 1 a and 1 band a single reel (not shown) around which a magnetic tape is wound andwhich is supported for rotation in the cartridge casing 1. A tape outletopening 2 through which the magnetic tape is drawn out is formed in oneend face of the cartridge casing 1 near a corner thereof. A slide door 3for opening and closing the tape outlet opening 2 is mounted in thecartridge casing 1 to be slidable back and forth between a closingposition where it closes the tape outlet opening 2 and opening positionwhere it opens the same. The slide door 3 is urged toward the closingposition and held there by a spring disposed between a side face of thecartridge casing 1 and the rear end face of the slide door 3 as will bedescribed in detail later.

[0098] As shown in FIG. 2, a leader pin 4 fixed to the leading end ofthe magnetic tape is held inside the tape outlet opening 2. When themagnetic tape cartridge is loaded in a tape drive system, a reel drivemeans of the tape drive system is brought into engagement withengagement teeth (not shown) on the reel which is exposed in the bottomface of the cartridge casing 1 at the center thereof and a tape drawingmechanism of the tape drive system pushes the front end face 3 a of theslide door 3 to open the slide door 3. Further the tape drawingmechanism chucks the leader pin 4 and pulls the leader pin 4 into thesystem, whereby the magnetic tape is set in the tape drive system sothat data can be recorded on or read out from the magnetic tape.

[0099] A knob 5 for inhibiting erasure and write projects outside in oneside face of the cartridge casing 1.

[0100] As shown in FIG. 5, guide grooves 1 c and 1 d for guiding theupper end lower ends of the slide door 3 are formed on the upper andlower casing halves 1 a and 1 b.

[0101] As shown in FIGS. 3, 4A and 4B, a door spring 6 for urging theslide door 3 toward the closing position and holding the slide door 3 inthe closing position is provided in the passage of the slide door 3inside the cartridge casing 1. The door spring 6 is a plate spring or awire spring and one end portion 6 a of the door spring 6 is held betweenthe upper and lower casing halves 1 a and 1 b. More specifically, a rib7 extends upward from the bottom of the lower casing 1 b, and a hole 7 ais formed in the rib 7. The door spring 6 comprises a vertical endportion (said one end portion) 6 a, an arcuate end portion 6 b and ahorizontal middle portion connecting the end portions 6 a and 6 b. Thevertical end portion 6 a of the door spring 6 is inserted into the hole7 a so that the horizontal middle portion rests on the top of the rib 7and the arcuate end portion 6 b abuts against the rear end face 3 b ofthe slide door 3 as shown in FIGS. 4A and 4B. A part of the upper casinghalf 1 a is disposed in contact with or near the horizontal middleportion of the door spring 6, thereby holding the vertical end portion6a in the hole 7.

[0102] When the door spring 6 is a plate spring, the rear end face 3 bof the slide door 3 may be flat as shown in FIG. 6A, but when the doorspring 6 is a wire spring, it is preferred that the rear end face 3 b ofthe slide door 3 be recessed as shown in FIG. 6B.

[0103] By increasing the parts of the door spring 6 which contributes toresiliency of the slide door 6 as shown in FIGS. 7A and 7B, the strokeof the slide door 6 can be enlarged. In this case, a rib 8 may be formedon the upper casing half 1 a to extend downward to hold the bightportion of the door spring 6 between the lower surface of the rib 8 andthe upper surface of the rib 7 on the lower casing half 1 b.Accordingly, the end portion of the door spring 6 can be held even ifthe end portion is not straight and even if the rib 7 is not providedwith the hole 7 a.

[0104] In either case, the door spring 6 can be incorporated in thecartridge casing 1 by simply positioning the door spring 6 in apredetermined position on the lower casing half 1 b and fixing the uppercasing half 1 a onto the lower casing half 1 b.

[0105] When a wire spring is employed as the door spring 6, an innerwall 9 of a predetermined height may be provided on the cartridge casing1 along the passage of the slide door 3 so that the door spring 6 isconstantly positioned between the inner wall 9 and an outer wall 10 asshown in FIG. 8, whereby the door spring 6 can be prevented from beingdisengaged from the slide door 3.

[0106] Further when a wire spring is employed as the door spring 6, thedoor spring 6 may be held at its one end by fitting a loop 6 c (FIG. 9)formed on its rear end portion on a projection 7 b formed on the top ofthe rib 7 which is fitted in a recess 8 a formed in the lower end faceof the rib 8 extending downward from the upper casing half 1 a.

[0107] A magnetic tape cartridge in accordance with a second embodimentof the present invention will be described with reference to FIGS. 10 to12, hereinbelow.

[0108] In the second embodiment, an inner wall 9 is formed along thepassage of the slide door 3 opposed to an outer wall 10 and a closedspace 11 defining the passage of the slide door 3 is formed between theupper and lower casing halves 1 a and 1 b and the rear end face 3 b ofthe slide door 3, and a door spring 6 in the form of a plate springshaped as shown in FIGS. 11A and 11B is disposed inside the closed space11 with its one end in abutment against the rear end face 12 of theclosed space 11 and its the other end in abutment against the rear endface 3 b of the slide door 3.

[0109] With this embodiment, the door spring 6 need not be held on thecartridge casing 1 but may be simply thrown in the closed space 11, andaccordingly incorporation of the door spring 6 is extremely facilitated.

[0110] Further in this embodiment, the front end portion of the slidedoor 3 is bent outward in a L-shape as indicated at 3 c in FIG. 10 sothat the door opening means of the tape drive system can abut againstthe slide door 3 in a larger area and the slide door 3 can be surelyopened.

[0111] In addition to the wire spring and the plate spring, a coiledspring may be employed as the door spring 6. In the third embodimentshown in FIGS. 13 and 14, the door spring 6 is in the form of a coiledspring and is held in place by forming an elongated space 13 whichextends in parallel to the direction of movement of the slide door 3between a rib 7 extending upward from the lower casing half 1 b and arib 8 extending downward from the upper casing half la and inserting therear end portion of the door spring 6 into the elongated space 13.

[0112] Further when a coiled spring is employed as the door spring 6,the rear end portion of the slide door 3 may be bent in a L-shape asindicated at 3 d in FIG. 15 so that the door spring 6 can abut againstthe slide door 3 in a larger area.

[0113] A magnetic tape cartridge in accordance with a fourth embodimentof the present invention will be described with reference to FIGS. 16A,16B, 17A and 17B, hereinbelow.

[0114] As shown in FIGS. 16A, 16B, 17A and 17B, in this embodiment, theslide door 3 is urged toward the closing position and held there by acorrugated door spring 6. P denotes the passage of the slide door 3. Theslide door 3 is provided with a recess 3 a which extends toward thefront end face 3 a of the slide door 3 from the read end face 3 b. Thefront half of the corrugated door spring 6 is inserted into the recess 3c with the rear end of the door spring 6 abutting against the rear innersurface 1 e of the cartridge casing 1 and the front end of the doorspring 6 abutting against the bottom surface 3 d of the recess 3 c.

[0115] With this arrangement, even in the state where the slide door 3is opened and the distance between the rear end face 3 b of the slidedoor 3 and the rear inner surface 1 e of the cartridge casing 1 isshortened with the door spring 6 compressed as shown in FIG. 16B, thedoor spring 6 can exhibit a desired urging force.

[0116] A recess 3 e which opens only in the rear end face 3 b of theslide door 3 as shown in FIGS. 18A and 18B may be formed instead of therecess 3 c which opens both in the rear end face 3 b and a side face ofthe slide door 3.

[0117] In a fifth embodiment of the present invention shown in FIG. 19,a cutaway portion 3 f is formed on an upper part of the slide door 3 andthe front half of a coiled door spring 108 is placed on the cutawayportion 3 f. The front end of the door spring 108 is in abutment againstthe front end face 3 g of the cutaway portion 3 f and the rear end ofthe door spring 108 is in abutment against a wall portion 109 formed onthe upper casing half 1 a. reference numeral 10 denotes a rib fortacking the door spring 108.

[0118] The sixth embodiment shown in FIGS. 20A and 20B is differs fromthe fourth embodiment shown in FIGS. 16A, 16B, 17A and 17B in that thedoor spring 6 is formed by a pair of spring members 6A and 6B connectedin series with a slide plate 111 intervening therebetween and the frontspring member 6A is larger that the rear spring member 6B in the urgingforce.

[0119] In this embodiment, when the slide door 3 is opened overcomingthe force of the door spring 6, the rear spring member 6B, which isweaker than the front spring member 6A, is first compressed and then thefront spring member 6A is compressed, whereby a relatively constantspring characteristic can be obtained over the entire stroke of theslide door 3, and adjustment of the door opening force can befacilitated.

[0120] In the seventh embodiment shown in FIGS. 21A and 21B, the doorspring 6 is formed by a pair of spring members 6A and 6B which aredisposed in parallel in the passage P of the slide door 3 and the upperspring member 6A is shorter than the lower spring member 6B.

[0121] In this embodiment, for example when an obstacle such as a recess112 exists in the upper casing half 1 a, a short and narrow springmember 6A is disposed in the upper casing half 1 a and a long and narrowspring member 6B is disposed in the lower casing half 1 b, whereby adesired urging force is obtained in total.

[0122] In the eighth embodiment shown in FIGS. 22A and 22B, the doorspring 6 is formed by a plurality (three in the illustrated embodiment)of elastic rings 113 such as rubber rings arranged in series in theslide door passage P.

[0123] The elastic rings are easy to produce and since they keeps anurging force until they compressed flat as shown in FIG. 22B, a doorspring having a long stroke and a desired urging force can be easilyobtained.

[0124] The ninth embodiment shown in FIGS. 23A and 23B is similar to theeighth embodiment but a plurality of helical elastic members 14 areemployed in place of the elastic rings 113.

[0125] In the tenth embodiment shown in FIGS. 24A to 24D, a corrugatedwire spring 16 having a pair of coiled portions 16 a and 16 b is used asa door spring 6.

[0126] In this embodiment, when the slide door 3 is opened and as thewire spring 16 is increasingly compressed, bent portions of the wirespring 16 are rotated about the coiled portions 16 a and 16 b and cometo cross each other as shown in FIGS. 24B to 24D, whereby a long strokecan be obtained.

[0127] The wire spring 16 may be provided with a single or three or morecoiled portions. By changing the number of the coiled portions, a springmember 16 having a desired spring characteristics can be obtained.Further by changing the number of turns of the coiled portion, a springmember 16 having a desired spring characteristics can also be obtained.

[0128] A magnetic tape cartridge in accordance with an eleventhembodiment of the present invention will be described with reference toFIGS. 25 (25A and 25B) to 28, hereinbelow. In this embodiment, a pair ofcoiled springs 20 are employed as the door spring 6.

[0129] Since the slide door 3 is slid over a relatively long distance,there is fear that the coiled springs 20 buckles when the slide door 3is opened. In this embodiment, buckling of the coiled springs 20 isprevented by mounting a spring retainer plate 18 on the rear end of theslide door 3.

[0130] That is, as shown in FIG. 26, the spring retainer plate 18 hasupper and lower edges 18 a which are substantially parallel to thedirection of sliding movement of the slide door 3 and is mounted on therear end of the slide door 3 to extend in the door passage P.

[0131] Further, as shown in FIGS. 25A and 25B, the slide door passage Pis provided with an extension 19 which is narrower than the slide doorpassage P and extends away from the slide door 3. The spring retainerplate 18 is narrower than the slide door 3 and is inserted into theextension 19. Then as shown in FIG. 27, the coiled springs 20 arecontained in the spaces surrounded by the upper and lower edges 18 a ofthe spring retainer plate 18 and the walls of the slide door passage P.

[0132] Accordingly, even if the coiled springs 20 are compressed inresponse to opening the slide door 3, the coiled springs 20 cannotbuckle and can keep their longitudinal axes in the direction of slidingmovement of the slide door 3.

[0133] Further since a locator notch 17 and the like are generallypositioned behind the slide soor passage P, the extension 19 is curvedinward to clear the notch 17 and the spring retainer plate 18 is formedof a flexible material so that it can slide along the curved extension19 as shown in FIG. 28.

[0134] In the twelfth embodiment shown in FIGS. 29A, 29B and 30, asingle coiled spring 20 is employed as the door spring. A pair ofgrooves 21 are formed on opposite side walls of the slide door passage Popposed to each other as shown in FIG. 30. BY the grooves 21, a spacefor containing the coiled spring 20 having a width 1 larger than thespace a between the side walls is defined and the coiled spring 20 iscontained in the space.

[0135] With this arrangement, not only buckling of the coiled spring 20is prevented but also freedom of selecting the coiled spring 20 isincreased since a coiled spring larger than the space a in diameter canbe used.

[0136] Further even if notches 17′ for locating or handling the magnetictape cartridge are disposed behind the slide door passage P, the coiledspring 20 can extend along the entire length of the cartridge casing 1as shown in FIG. 31.

[0137] The grooves 21 may be formed between the upper and lower casinghalves 1 a and 1 b. However, by forming a main part of the groove 21 inone of the upper and lower casing 1 a and 1 b as shown in FIG. 30, thecartridge casing 1 can be assembled with the coiled spring 20 held inthe casing half where the main part of the groove 21 is formed, assemblyof the cartridge casing 1 is facilitated.

[0138] In the thirteenth embodiment shown in FIGS. 32A, 32B, 33, 34A,34B and 34C, a coiled spring 20 is also employed and buckling of thecoiled spring 20 is prevented by a spring support rod 22.

[0139] That is, the spring support rod 22 extends rearward from the readend of the slide door 3 and the coiled spring 20 is fitted on the rod22.

[0140] Also in this embodiment, a pair of grooves 21 are formed onopposite side walls of the slide door passage P opposed to each other asshown in FIG. 34C. BY the grooves 21, a space for containing the coiledspring 20 having a width larger than the space between the side walls isdefined and the coiled spring 20 is contained in the space.

[0141] With this arrangement, not only buckling of the coiled spring 20is prevented but also freedom of selecting the coiled spring 20 isincreased since a colied spring larger than the space in diameter can beused. A wall 23 is formed in the cartridge casing 1 to form a springseat behind the slide door passage P and the spring support rod 22 isinserted into an axial hole 23 a formed in the wall 23. It is preferredthat the spring support rod 22 be provided with a pair of flat surfaceson opposite sides thereof and the axial hole 23 a conforms to the rod 22in shape as shown in FIG. 34A to 34C. With this arrangement, the end ofthe coiled spring 22 from entering the space between the axial hole 23 aand the rod 22 and since the area of the spring seat is increased, theend of the coiled spring 20 can be stably supported.

[0142] By virtue of the spring support rod 22, the coiled spring 22 canbe easily incorporated in, for instance, the lower casing half 1 b asshown in FIG. 35A. However without the spring support rod 22, the coiledspring 20 is apt to buckle as shown in FIG. 35B when incorporating inthe lower casing half 1 b, which makes difficult incorporation of thecoiled spring 20.

[0143] When a recess 3 c is formed on the rear end face of the slidedoor 3, the spring support rod 22 projects from the bottom surface 3 dof the recess 3 c, and the coiled spring 20 is fitted on the rod 22 withone end in contact with the bottom surface 3 d and the other end incontact with the inner wall surface 1 e of the cartridge casing 1 asshown in FIGS. 36 and 37, the stroke of the coiled spring 20 can beincreased and the freedom of selecting the coiled spring can beenlarged.

[0144] Further by providing a shoulder 22 a on the tip of the springsupport rod 22 as shown in FIG. 38 and tacking the coiled spring on therod 22, incorporation of the coiled spring 20 is facilitated. When thetip portion of the rod 22 is smaller in diameter than the body portionof the rod 22, fitting the coiled spring on the rod 22 by an automatedassembling system is facilitated.

[0145] It is preferred than the tip portion be bifurcated into a pair ofresilient pieces 22 b as shown in FIG. 39A. In this case, the rod 22 canbe easily inserted into the axial hole 23 a by virtue of resilientdeformation of the resilient pieces 22 b even if the axial hole 23 a issmall as shown in FIG. 39B.

[0146] The axial holes 23 a may be of such a diameter that permitsinsertion of the rod 22 without deformation of the resilient pieces 22 bas shown in 39C. Also in this case, by providing the spring support rod22 with a pair of flat surfaces on opposite sides thereof and shapingthe axial hole 23 a to conform to the rod 22 in shape, the end of thecoiled spring 20 can be stably supported by the wall 23.

[0147] Further by providing the coiled spring 20 with a plurality ofclose winding portions 20 a as shown in FIG. 40, rigidity of the coiledspring 20 is increased, which contributes to prevention of buckling ofthe coiled spring 20.

[0148] Though it is preferred that the spring support rod 22 be formedintegrally with the slide door 3 so that the number of parts is reduced,the rod 22 may be formed separately from the slide door 3 as shown inFIGS. 41A to 41C. FIG. 41C is a fragmentary plan view of an importantpart of the rod 22, FIG. 41B is a side view of the rod 22 and FIG. 41Cis a fragmentary cross-sectional view of an important part of the slidedoor 3. The rod 22 comprises a body portion 22 c having a tip portionsuch as shown in FIG. 39A, a small diameter portion 22d formed near thebase end of the body portion 22 c and a base end portion 22 e connectedto the small diameter portion 22 d as shown in FIG. 41A. The base endportion 22 e is provided with a pair of flat portions on opposite sidesthereof as shown in FIG. 41B in order to prevent rotation of the rod 22.The rear end portion of the slide door 3 is provided with an engagementrecess 24 which conforms to the shape of the base end portion 22 e ofthe rod 22 as shown in FIG. 41C. After the coiled spring 20 is fitted onthe rod 22 from the base end portion 22 e, the base end portion 22 e isbrought into engagement with the recess 24 of the slide door 3 fromabove, whereby the rod 22 is fixed to the slide door 3 as shown in FIG.42.

[0149] A fourteenth embodiment of the present invention will bedescribed with reference to FIGS. 43, 44A, 44B and 45, hereinbelow. FIG.43 is a perspective view showing incorporation of a door unit in thecartridge casing, FIG. 44A is a front cross-sectional view showing thedoor unit in a state where the slide door is in a tacked state, FIG. 44Bis a front cross-sectional view showing the door unit in a state wherethe slide door is slidable, and FIG. 45 is a cross-sectional view takenalong line A-A in FIG. 44B.

[0150] In this embodiment, the side walls of the cartridge casing 1 onwhich the slide door 3 is to be mounted is removed and a door unit 30 ismounted on the side of the cartridge casing 1. The door unit 30comprises a casing 25 and a slide door 3 and a plurality of coiledsprings 20 incorporated in the casing 25 and is fixed to the cartridgecasing 1 by bonding or press-fitting. The casing 25 is provided with anopening 25 a which forms the tape outlet opening 2.

[0151] The door unit 30 is provided with a tacking mechanism for holdingthe slide door 3 not to be ejected from the casing 25 under the force ofthe coiled springs 20 after the coiled springs 20 are incorporated inthe casing 25.

[0152] As shown in FIGS. 44A and 44B, the tacking mechanism comprises apair of engagement projections 25 b formed on the top surface and thebottom surface of the slide door passage and a pair of engagementrecesses 3 f formed on the upper and lower edges of the slide door 3.After the coiled springs 20 are incorporated in the slide door passage,the slide door 3 is inserted into the slide door passage from theopening at the right side end of the casing 25 to a position where theengagement projections 25 b and the engagement recesses 3 f are broughtinto engagement with each other as shown in FIG. 44A. Thus the slidedoor 3 is tacked and the door unit 30 is incorporated in the cartridgecasing 1 in this state. Then by pushing leftward the slide door 3 todisengage the engagement projections 25 b and the engagement recesses 3f from each other as shown in FIG. 44B, the slide door 3 comes to beslidable.

[0153] In order to more stabilize the sliding movement of the slide door3, a plurality of ribs 25 c extending in the direction of the slidingmovement of the slide door 3 are formed on opposite sides of the slidedoor passage as shown in FIG. 45.

[0154] In the fifteenth embodiment shown in FIGS. 46A and 46B, acorrugated wire spring 26 is employed as the door spring. In order toprevent the end portion of the wire spring 26 from entering the spacebetween the slide door 3 and the inner surface of the cartridge casing1, the end portion of the wire spring 26 is bent along the rear end faceof the slide door 3 to form a bent portion 27 as shown in FIG. 46B.

[0155] In the sixteenth embodiment shown in FIGS. 47A and 47B, a coiledspring 28 provided with an annular portion which is of a rectangle orellipsoid conforming to the cross-sectional shape of the slide door 3 asshown in FIG. 47B is employed as the door spring. With this arrangement,buckling of the coiled spring 28 is prevented and incorporation of thespring 28 is facilitated.

[0156] In the seventeenth embodiment shown in FIG. 48A and 49, the doorspring is formed by a coiled spring 32 and a plate spring 31 isconnected to one end of the coiled spring 32. The plate spring 31comprises a central portion 31 a provided at its center with anengagement projection 31 b with which the end of the coiled spring 32 isengaged and a pair of wings 31 c which extend toward the slide door 3form opposite ends of the central portion 31 a. The end portions of thewings 31 c are engaged with engagement projections 3 g formed on theupper and lower edges of the slide door 3.

[0157] The plate spring 31 may be provided on each end of the coiledspring 32 as shown in FIG. 48B.

[0158] In this embodiment, the coiled spring 32 may be smaller in lengthby the length of the plate spring 31 and the coiled spring 32 becomesless apt to buckle. Further freedom in designing the door spring isincreased by combination of the coiled spring 32 and the plate spring31.

[0159] That is, in the case where only a coiled spring used, therelation between the urging force of the spring and the displacement ofthe spring is linear as shown in FIG. 50A whereas, in the case of acombination of a coiled spring and a plate spring or plate springs, therelation is represented by a broken line as shown in FIGS. 50B and 50C,which increases freedom in designing the door spring.

[0160] In the eighteenth embodiment shown in FIGS. 51A and 51B, theslide door 3 is formed by plastic molding and the door spring is formedby an elastic body 106 integrally molded with the slide door 3. In thisparticular embodiment, the elastic body 106 is substantially S-shaped.However the elastic body 106 may be of various shapes such as thoseshown in FIGS. 52A to 52C so long as it can urges the slide door 3toward the closing position.

[0161] By forming the door spring by such an elastic body integrallyformed with the slide door, the number of parts can be reduced andassembly of the magnetic tape cartridge is facilitated.

[0162] A nineteenth embodiment of the present invention will bedescribed with reference to FIGS. 53 and 54, hereinbelow.

[0163] The magnetic tape cartridge of this embodiment is provided with aslide door lock mechanism for locking the slide door in the closingposition in such a manner that the lock mechanism is automaticallyreleased when the slide door is pushed toward the opening position.

[0164] In this embodiment, a locking means which is brought intoengagement with the slide door in response to return of the slide doorto the closing position under the urging force of the door spring andlocks the slide door in the closing position is provided on thecartridge casing and the working surface on which the tape drawingmechanism pushes the slide door toward the opening position is inclinedso that a force pushing the slide door toward the opening positiongenerates a component which displaces the slide door in a direction inwhich the slide door is disengaged from the locking means on thecartridge casing.

[0165] With this arrangement, the locking means is automaticallydisengaged from the slide door to permit the door to slide when theslide door is pushed toward the opening position.

[0166] As shown in FIG. 53, the front end face 3 a of the slide door 3is provided with an inclined surface 207 as a working surface on whichthe tape drawing mechanism of the tape drive system acts. When themagnetic tape cartridge is loaded in the tape drive system in thedirection of arrow A, a pusher in the tape drive system pushes theinclined surface 207 to open the slide door 3 overcoming the force ofthe door spring.

[0167] An engagement projection 208 having a vertical surface 208 afacing toward the opening position of the slide door 3 and an inclinedsurface 208 b which gently slopes downward to the inclined workingsurface 207 is formed on the back side of the slide door 3 near thefront end face 3 a.

[0168] A locking piece 209 having a vertical surface 209 a which isengaged with the vertical surface 208 a of the engagement projection 208to lock the slide door 3 in the closing position extends from the innersurface 1 e of the cartridge casing 1.

[0169] When the slide door 3 is returned to the closing position underthe force of the door spring, the inclined surface 208 b is brought intoabutment against the lower end of the locking piece 209 and the frontend portion of the slide door 3 and/or the locking piece 209 isresiliently deflected to permit the slide door 3 to return to theclosing position. When the slide door 3 reaches the closing position,the front end portion of the slide door 3 and/or the locking piece 209are resiliently returned to the original position and the verticalsurfaces 208 a and 209 a are brought into engagement with each other tolock the slide door 3 in the closing position.

[0170] When a force in the direction of arrow B in FIG. 54 acts on theinclined working surface 207 during loading the magnetic tape cartridgein the tape drive system, a component which displaces outward the frontend portion of the slide door 3 is generated and the vertical surfaces208 a and 209 a are automatically disengaged from each other to permitthe slide door 3 to slide toward the opening position.

[0171] The engagement projection 208 and the locking piece 209 may haveinclined engagement surfaces 208 c and 209 b as shown in FIG. 55 inplace of the vertical engagement surfaces 208 a and 209 a. Further arecess 208 d may be formed on the base of the engagement projection 208as shown in FIG. 56 so that the engagement projection 208 can be moreeasily deflected.

[0172] A twentieth embodiment of the present invention will be describedwith reference to FIGS. 57 to 59, hereinbelow.

[0173] The magnetic tape cartridge of this embodiment is also providedwith a slide door lock mechanism for locking the slide door in theclosing position in such a manner that the lock mechanism isautomatically released when the slide door is pushed toward the openingposition.

[0174] As shown in FIG. 57, the slide door 3 is provided at its frontend with a locking member 307 for locking the slide door 3 in theclosing position.

[0175] The locking member 307 is formed integrally with the slide door 3and comprises a flexible leg 307 a, an engagement projection 307 bformed on the tip of the leg 307 a to face upward, and a working portion307 c which extends downward from the tip of the leg 307 a and receivesan external force when the slide door 3 is opened. As the magnetic tapecartridge is loaded in the tape drive system, a pusher in the tapedriving system pushes the working portion 307 c to open the slide door3.

[0176] A recess 308 is formed in the front end face of the cartridgecasing so that the front end portion of the slide door 3 is received inthe recess 308 when the slide door 3 is in the closing position. Anengagement recess 309 which is adapted to engage with the engagementprojection 307 b is formed on the upper surface 308 a of the recess 308.

[0177] When the slide door 3 is moved from the position shown in FIG. 57to the closing position under the force of the door spring, theengagement projection 307 b is brought into abutment against the uppersurface 308 a of the recess 308. At this time, the leg 307 a of thelocking member 307 is deflected downward and the engagement projection307 b is brought into engagement with the engagement recess 309 to lockthe slide door 3 in the closing position as shown in FIG. 58.

[0178] When the magnetic tape cartridge is loaded in the tape drivesystem, the pusher in the tape drive system pushes the working portion307 c in the direction of the arrow in FIG. 59 and the leg 307 a isdeflected downward to disengage the engagement projection 307 b from theengagement recess 309, thereby permitting the slide door 3 to slidetoward the opening position as shown in FIG. 59.

[0179] In the twenty-first embodiment of the present invention shown inFIG. 60, the slide door 403 is not provided with a door spring and ismoved back and forth along the slide door passage P by a drive member inthe tape drive system which pushes and pulls a knob 403 a at the frontend of the slide door 403.

[0180] The slide door 403 is curved inward (upward as seen in FIG. 60)and an engagement projection 403 b is formed at the rear end of theslide door 403. When the slide door 403 is in the closing position, theengagement projection 403 b is in engagement with a recess 411 formed onan inner wall of the door passage P. When the slide door 403 is pushedtoward the opening position, the slide door 403 is resiliently deflectedoutward and the engagement projection 403 b is disengaged from therecess 411. When the slide door 403 reaches the opening position, theengagement projection 403 b is brought into engagement with anotherrecess 412 formed on the inner wall and locks the slide door 403 in theopening position. When the slide door 403 is pulled toward the closingposition, the slide door 403 is resiliently deflected outward and theengagement projection 403 b is disengaged from the recess 412.

[0181] A magnetic tape cartridge in accordance with a twenty-secondembodiment of the present invention will be described with reference toFIG. 61.

[0182] The magnetic tape cartridge of this embodiment is characterizedin that the sliding door is provided with a means for reducing theresistance to slide.

[0183] As shown in FIG. 61, the slide 503 is provided with a pair ofprotrusions 503 b on each of the upper and lower edges (slide surfaces).The protrusions 503 b are U-shaped in cross-section. When the slide door503 is slid between the closing position and the opening position, onlythe protrusions 503 b are in contact with the slide surfaces of theslide passage, whereby the contact area between the slide door 503 andthe sliding surfaces of the passage is reduced and the resistance toslide therebetween is reduced.

[0184] The slide 503 may be provided with protrusions 503 d which areV-shaped in cross-section as shown in FIG. 62 in place of theprotrusions 503 b which are U-shaped in cross-section.

[0185] Further in place of forming protrusions which are U-shaped orV-shaped in cross-section, the upper and lower sliding surfaces may becontinuously U-shaped or V-shaped in cross-section as indicated at 503 eand 503 f in FIGS. 63 and 64.

[0186] In the modification shown in FIG. 65, the slide 503 is providedwith a pair of semi-spherical projections 503 g on each of the upper andlower slide surfaces.

[0187] In the modification shown in FIGS. 66 and 67, a narrow protrusion503 h is formed on each of the sliding surfaces of the slide door 503 toextend over the entire length of the sliding surface.

[0188] As shown in FIG. 67, each of the upper and lower sliding surfaces507 a of the slide door passage 307 is provided with a recess 507 bextending over the entire length of the sliding surfaces 507 a. Theprotrusions 503 h are received in the recesses 507 b. With thisarrangement, the resistance to slide is reduced and at the same time,since the protrusions 503 h are received in the recesses 570 b,dust-proof effect is increased.

[0189] The protrusion 503 h may be discontinuous as shown in FIG. 67.

[0190] Further, the sliding surfaces of the slide door 503 may beprovided with recesses 503 i and the sliding surfaces of the slide doorpassage 507 may be provided with narrow protrusions 507 c as shown inFIGS. 69 and 70.

[0191] Further the sliding surfaces of the slide door passage 507 may beprovided with narrow protrusions 507 c with the sliding surfaces of theslide door 503 kept flat as shown in FIG. 71.

[0192] It is preferred that the protrusions on the sliding surfaces ofthe slide door 503 and/or the protrusions on the sliding surfaces of theslide door passage be chamfered, rounded or rounded into a ball-likeshape.

[0193] A magnetic tape cartridge in accordance with a twenty-thirdembodiment of the present invention is provided with a slide door 603formed of metal shown in FIGS. 72A to 72D.

[0194] The slide door 603 has upper and lower edges 603 c and 603 dwhich are folded as shown in FIG. 72C. The front and read end portionsof the slide door 603 including the front and rear end faces 603 a and603 b are pressed by dies or the like so that the end portions areslightly tapered as shown in FIG. 72D.

[0195] With this arrangement, the curved surfaces of the upper and loweredges 603 c and 603 d abut against the tape outlet opening 2 and the endportions of the upper and lower edges 603 c and 603 d are brought intoabutment against the tape outlet opening 2, whereby the tape outletopening 2 is prevented from being cut by a cut surface of metal.

[0196]FIG. 73 is an enlarged perspective view of a part of the magnetictape cartridge shown in FIG. 1. As shown in FIG. 73, the outer surface 3d and the front end face 3 a of the slide door 3 are positioned insidethe outer surface of the cartridge casing 1. That is, the outer surface3 d is arranged to slide on the inner surface of the cartridge casing 1.Further a pair of cutaway portions 3 c are formed on the front endportion of the slide door 3 as shown in FIG. 74 and when the slide door3 is in the closing position, the cutaway portions are in contact withthe inner surface of the cartridge casing 1. The depth of the cutawayportion i3 c is selected so that the front end face 3 a is positionedinside the outer surface of the cartridge casing 1 as shown in FIG. 73.

[0197] With this arrangement, impact does not directly act on the slide,for instance, when the magnetic tape cartridge is dropped onto thefloor, whereby the slide door 3 is prevented from being broken.

[0198] In the case where the slide door 3 is provided with a notchportion 3 e for facilitating opening of the slide door 3 as shown inFIG. 75, it is preferred that also the outer surface of the notchportion 3 e be positioned inside the outer surface of the cartridgecasing 1 as shown in FIG. 76.

What is claimed is;
 1. A magnetic tape cartridge comprising a cartridgecasing formed by upper and lower casing halves and a single reel aroundwhich a magnetic tape is wound and which is contained in the cartridgecasing for rotation, wherein the improvement comprises that a slide doorfor opening and closing a tape outlet opening is mounted on thecartridge casing to be linearly slidable along a door passage between aclosing position where it closes the tape outlet opening and an openingposition where it opens the tape outlet opening, and a door spring forurging the slide door toward the closing position and holding the samein the closing position is disposed on the door passage.
 2. A magnetictape cartridge as defined in claim 1 in which guide grooves for guidingthe upper end lower ends of the slide door along the door passage areformed respectively on the upper and lower casing halves and the doorspring is in the form of a wire spring or a plate spring which is heldbetween the upper and lower casing halves at one end and abuts againstthe rear end face of the slide door at the other end.
 3. A magnetic tapecartridge as defined in claim 1 in which a wall portion which preventsthe door spring from being disengaged from the slide door while theslide is slid between the opening position and the closing position isprovided in the cartridge casing.
 4. A magnetic tape cartridge asdefined in claim 1 in which a closed space defining the door passage isformed between the upper and lower casing halves and the rear end faceof the slide door and the door spring in the form of a plate spring isdisposed in the closed space with its ends in abutment against the endwall of the closed space and the rear end face of the slide door,respectively.
 5. A magnetic tape cartridge as defined in claim 1 inwhich the door spring is a coiled spring whose longitudinal axis extendsin parallel to the direction of sliding movement of the slide door.
 6. Amagnetic tape cartridge as defined in claim 5 in which the coiled springis disposed in a space surrounded by ribs respectively extending fromthe upper and lower casing halves.
 7. A magnetic tape cartridge asdefined in claim 5, in which a bent portion against which the coiledspring abuts is formed on a rear end portion of the slide door.
 8. Amagnetic tape cartridge as defined in claim 1 in which the door springis disposed on the door passage with its one end portion received in arecess formed in the slide door.
 9. A magnetic tape cartridge as definedin claim 1 in which the door spring comprises a plurality of springelements which are different in strength and are arranged in seriesalong the door passage.
 10. A magnetic tape cartridge as defined inclaim 1 in which the door spring comprises a plurality of springelements which are different in strength and are arranged in parallelalong the door passage.
 11. A magnetic tape cartridge as defined inclaim 1 in which the door spring comprises a plurality of elastic ringmembers which are arranged in series along the door passage.
 12. Amagnetic tape cartridge as defined in claim 1 in which the door springcomprises a corrugated wire spring having at least one coiled portion.13. A magnetic tape cartridge as defined in claim 1 in which a springretainer plate which has upper and lower edges which are substantiallyparallel to the direction of sliding movement of the slide door ismounted on the slide door to extend in the door passage and the doorspring in the form of a coiled spring is contained in a space surroundedby the edge of the spring retainer plate and a wall defining the doorpassage.
 14. A magnetic tape cartridge as defined in claim 13 in whichthe spring retainer plate is flexible.
 15. A magnetic tape cartridge asdefined in claim 1 in which a pair of grooves are formed on oppositeside walls of the door passage to extend in the direction of the slidingmovement of the slide door opposed to each other and the door spring inthe form of a coiled spring is contained in the space formed between thegrooves.
 16. A magnetic tape cartridge as defined in claim 1 in which aspring support rod extends in the door passage from the slide door inparallel to the direction of sliding movement of the slide door and thedoor spring in the form of a coiled spring is fitted on the springsupport rod.
 17. A magnetic tape cartridge as defined in claim 16 inwhich a part of the door spring is received in a recess formed in theslide door.
 18. A magnetic tape cartridge as defined in claim 16 inwhich the spring support rod is provided at its free end with aprojection for tacking the door spring on the rod.
 19. A magnetic tapecartridge as defined in claim 18 in which the projection is divided intoa plurality of resilient pieces.
 20. A magnetic tape cartridge asdefined in claim 1 in which the door spring comprises a corrugated wirespring and the end of the wire spring in contact with the slide door isbent in the direction of width of the slide door.
 21. A magnetic tapecartridge as defined in claim 1 in which the door spring comprises acoiled spring having an annular portion which conforms to a rectangularor ellipsoidal cross-section of the door passage.
 22. A magnetic tapecartridge as defined in claim 1 in which the door spring comprises acoiled spring extending in the direction of the sliding movement of theslide door and a plate spring connected to at least one end of thecoiled spring.
 23. A magnetic tape cartridge as defined in claim 1 inwhich the door spring is a plate spring and the rear end face of theslide door is flat.
 24. A magnetic tape cartridge as defined in claim 1in which the door spring is a wire spring and the rear end face of theslide door is recessed.
 25. A magnetic tape cartridge as defined inclaim 1 in which the door spring is a wire spring and an inner wall of apredetermined height is provided on the cartridge casing along thepassage of the slide door so that the door spring is constantlypositioned between the inner wall and an outer wall of the cartridgecasing.
 26. A magnetic tape cartridge as defined in claim 1 in which thedoor spring is a wire spring and the wire spring is held by fitting aloop formed on its one end portion on a projection formed on the top ofthe rib which extends upward from the lower casing half and is fitted ina recess formed in the lower end face of the rib extending downward fromthe upper casing half.
 27. A magnetic tape cartridge comprising acartridge casing and a single reel around which a magnetic tape is woundand which is contained in the cartridge casing for rotation, wherein theimprovement comprises that a door unit having a casing in which a slidedoor for opening and closing a tape outlet opening of the cartridgecasing and a door spring for urging the slide door toward the closingposition and holding the same in the closing position are incorporatedis mounted on one side of the cartridge casing.
 28. A magnetic tapecartridge as defined in claim 27 in which an engagement means whichtacks the slide door in a predetermined position overcoming the urgingforce of the door spring is provided between the casing of the door unitand the slide door.
 29. A magnetic tape cartridge comprising a cartridgecasing and a single reel around which a magnetic tape is wound and whichis contained in the cartridge casing for rotation, wherein theimprovement comprises that a slide door for opening and closing a tapeoutlet opening is mounted on the cartridge casing to be linearlyslidable along a door passage between a closing position where it closesthe tape outlet opening and an opening position where it opens the tapeoutlet opening, and a door spring for urging the slide door toward theclosing position and holding the same in the closing position is formedby an elastic member which is formed integrally with the slide door toextend rearward from the rear end of the slide door.
 30. A magnetic tapecartridge comprising a cartridge casing, a single reel around which amagnetic tape is wound and which is contained in the cartridge casingfor rotation, a slide door for opening and closing a tape outlet openingmounted on the cartridge casing to be linearly slidable between aclosing position where it closes the tape outlet opening and an openingposition where it opens the tape outlet opening, and a door spring forurging the slide door toward the closing position and holding the samein the closing position is disposed on the door passage, wherein theimprovement comprises that a locking means which is brought intoengagement with the slide door in response to return of the slide doorto the closing position under the urging force of the door spring andlocks the slide door in the closing position is provided on thecartridge casing and the working surface on which the slide door ispushed toward the opening position is inclined so that a force pushingthe slide door toward the opening position generates a component whichdisplaces the slide door in a direction in which the slide door isdisengaged from the locking means on the cartridge casing.
 31. Amagnetic tape cartridge comprising a cartridge casing, a single reelaround which a magnetic tape is wound and which is contained in thecartridge casing for rotation, a slide door for opening and closing atape outlet opening mounted on the cartridge casing to be linearlyslidable between a closing position where it closes the tape outletopening and an opening position where it opens the tape outlet opening,and a door spring for urging the slide door toward the closing positionand holding the same in the closing position is disposed on the doorpassage, wherein the improvement comprises that a flexible engagementmember which is brought into engagement with the cartridge casing inresponse to return of the slide door to the closing position under theurging force of the door spring and locks the slide door in the closingposition is provided on the slide door so that the engagement member isdeflected in a direction in which the engagement member is disengagedfrom the cartridge casing when a force pushing the slide door toward theopening position is applied to the engagement member.
 32. A magnetictape cartridge comprising a cartridge casing, a single reel around whicha magnetic tape is wound and which is contained in the cartridge casingfor rotation, a slide door for opening and closing a tape outlet openingmounted on the cartridge casing to be linearly slidable between aclosing position where it closes the tape outlet opening and an openingposition where it opens the tape outlet opening, wherein the improvementcomprises that a resilient engagement projection which is brought intoengagement with the cartridge casing to lock the slide door in theclosing position or the opening position is provided on the slide doorin such a manner that the engagement projection is deflected in adirection in which the engagement projection is disengaged from thecartridge casing when a force which moves the slide door toward theclosing position or the opening position is applied to the slide door.33. A magnetic tape cartridge comprising a cartridge casing, a singlereel around which a magnetic tape is wound and which is contained in thecartridge casing for rotation, and a slide door for opening and closinga tape outlet opening mounted on the cartridge casing to be linearlyslidable along a door passage between a closing position where it closesthe tape outlet opening and an opening position where it opens the tapeoutlet opening, wherein the improvement comprises that a sliding surfaceof the slide door which slides on a sliding surface of the door passageis protrudent.
 34. A magnetic tape cartridge comprising a cartridgecasing, a single reel around which a magnetic tape is wound and which iscontained in the cartridge casing for rotation, and a slide door foropening and closing a tape outlet opening mounted on the cartridgecasing to be linearly slidable along a door passage between a closingposition where it closes the tape outlet opening and an opening positionwhere it opens the tape outlet opening, wherein the improvementcomprises that a sliding surface of the slide door which slides on asliding surface of the door passage is provided with a protrusion.
 35. Amagnetic tape cartridge as defined in claim 34 in which the slide dooris provided with a plurality of discontinuous protrusions on eachsliding surface.
 36. A magnetic tape cartridge as defined in claim 34 inwhich the protrusion is rounded.
 37. A magnetic tape cartridgecomprising a cartridge casing, a single reel around which a magnetictape is wound and which is contained in the cartridge casing forrotation, and a slide door for opening and closing a tape outlet openingmounted on the cartridge casing to be linearly slidable along a doorpassage between a closing position where it closes the tape outletopening and an opening position where it opens the tape outlet opening,wherein the improvement comprises that a recess which extends in thedirection of sliding movement of the slide door is provided on one of asliding surface of the slide door and a sliding surface of the doorpassage opposed to the sliding surface of the slide door and aprotrusion in engagement with the recess is provided on the other.
 38. Amagnetic tape cartridge as defined in claim 37 in which the slidingsurfaces of the slide door is provided with recesses and the slidingsurfaces of the slide door passage is provided with narrow protrusionswhich can be fitted in the recesses in the sliding surfaces of the slidedoor.
 39. A magnetic tape cartridges as defined in claim 37 in which thesliding surfaces of the slide door passage are provided with narrowprotrusions and the sliding surfaces of the slide door are flat.
 40. Amagnetic tape cartridge comprising a cartridge casing, a single reelaround which a magnetic tape is wound and which is contained in thecartridge casing for rotation, and a slide door for opening and closinga tape outlet opening mounted on the cartridge casing to be linearlyslidable along a door passage, the slide door being formed of metal andat least a part of the upper and lower edges of the slide door beingfolded.
 41. A magnetic tape cartridge comprising a cartridge casing, asingle reel around which a magnetic tape is wound and which is containedin the cartridge casing for rotation, and a slide door for opening andclosing a tape outlet opening mounted on the cartridge casing to belinearly slidable along a door passage, wherein the improvementcomprises that the outer surface of the slide door is positioned insidethe outer surface of the cartridge casing.